A catalytic converter device, which has a tubular housing for guiding an exhaust gas flow, which the housing contains in an outlet section an SCR catalytic converter, wherein SCR denotes Selective Catalytic Reduction, is known from WO 2010/146285 A1. The housing has, in addition, an inlet section, which is arranged upstream of the outlet section in relation to the exhaust gas flow and contains an oxidation catalytic converter. An injection section is arranged between the inlet section and the outlet section, and another housing section designed integrally at the inlet section defines a channel of the injection section, which is likewise used to guide the exhaust gas flow. An injector port, at which an injector is connected for laterally injecting a liquid or gas into the exhaust gas flow, is arranged in the injection section laterally at the channel Lateral injection of the liquid, i.e., injection in such a way that a principal injection direction is sloped in relation to the axial direction of the channel, preferably in an angle range of 60° to 120°, especially in an angle range of 85° to 95° and preferably by about 90°, is brought about hereby. An injection chamber is formed in the channel of the injection chamber in the area of the injector port, the injection chamber being defined, on the one hand, by a perforated first partition, which is arranged upstream of the injector port in relation to the exhaust gas flow and through which the exhaust gas flow can flow, and, on the other hand, by a perforated second partition, which is arranged in the channel downstream of the injection section in relation to the exhaust gas flow and through which the exhaust gas flow can flow. The two partitions are designed and shaped in conjunction with their perforations in the prior-art catalytic converter device such that a swirling flow or turbulent flow or rotary flow, during which the entire exhaust gas flow rotates about the central longitudinal axis of the channel, develops in the injection chamber during the operation of the exhaust system. It is achieved hereby that a flow path in the injection chamber, which the exhaust gas flow follows from the first partition to the second partition, is at least 20% longer than an axial distance between the inlet section and the outlet section. A mixing section, in which the injected liquid can evaporate and mix with the exhaust gas flow, is created hereby.
The injected liquid is a reducing agent in an SCR system. An aqueous urea solution, which is ultimately converted by means of thermolysis and hydrolysis into ammonia and carbon dioxide in order to convert nitrogen oxides deposited in the SCR catalytic converter into nitrogen and water, is currently preferred in this case. On the one hand, the most complete evaporation possible of the reducing agent introduced in the liquid form is of decisive significance for the efficiency of such an SCR system. On the other hand, the most intense mixing possible of the evaporated reducing agent with the exhaust gas flow must be achieved as well.
As an alternative, a gaseous reducing agent, which is, for example, gaseous ammonia, may also be injected in modern SCR systems. It may be stored in this case in the form of solids, which are evaporated by means of heat supplied, for example, electrically, in order to generate the gaseous ammonia. The ammonia is thus available directly in the exhaust gas flow in these so-called Amminex systems, so that only an intensive mixing with the exhaust gas flow is necessary, because the evaporation already takes place in advance, outside the exhaust gas flow.